When plants get stress including environmental or biological stress from pathogenic bacteria, noxious insects, or viruses, oxygen inside which is an essential ingredient for a life changes into reactive oxygen species (ROS) such as superoxide anion radical (O2−), hydrogen peroxide (H2O2), hydroxyl radical, etc, causing serious disorders. In order to eliminate such active oxygen, a living body has macromolecular anti-oxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), peroxidase (POD) and catalase (CAT), and low molecular weight anti-oxidant substances such as vitamin C, vitamin E, glutathion, etc.
Peroxidase is an enzyme reducing hydrogen peroxide in the presence of electron donors, and is largely found in plant cells. Owing to its high sensitivity to enzyme reaction, peroxidase has been used as a reagent for many clinical tests. In addition to the importance in industry, peroxidase also draws an attention of scientists since it plays an important role in plant reaction against stress from outside. In general, the activity of plant peroxidase increases by various environmental stresses. In particular, plant culture cells show high activity of peroxidase because the cells are cultured under huge oxidative stress. According to an earlier report, peroxidase is mass-produced in sweetpotato culture cells more than in any other plant culture cells (Phytochemistry, 39, 981-984, 1995).
As of today, genes coding peroxidase included in some particular plants have been found in about 20 different plant species such as horseradish, barley, wheat, rape, Arabidopsis thaliana, tobacco, spinach, rice plant, etc. Recently, a total base sequence of Araidopsis has been identified, from which 73 peroxidase genes have been confirmed (Gene, 288, 129-138, 2002). But, the function of each individual peroxidase has not been explained yet. Peroxidase genes of a sweetpotato have been first reported by the present inventors. Particularly, the present inventors have separated three acidic peroxidase genes (swpa1, swpa2, swpa3) and a neutral peroxidase gene (swpn1) from sweetpotato culture cells, and have reported that those genes are expressed specifically in sweetpotato culture cells and found multiply in genome, and have further confirmed that peroxidase can be mass-produced stably by transfecting cells or plants with either some parts or a whole peroxidase gene (Mol. Gen. Genet., 255, 382-391, 1997; Mol. Genet. Genet., 261, 941-947, 1999).
In pervious studies, the present inventors separated novel acidic peroxidase genes ‘swpa4, ‘swpa5, and ‘swpa6’ along with basic peroxidase genes ‘swpb1’, ‘swpb2’ and ‘swpb3’ whose base sequences were all disclosed (Korea Patent Application #2003-28811; Mol. Genet. Genomics, 261, 941-947, 2003). Swpa4 was expressed strongly in sweetpotato culture cells but was not expressed in normal plant tissues. Swpa4 was highly expressed not only by biological stress like pathogenic bacteria (Pectobacterium chrysanhemi, KCTC 2569) but also by non-biological stresses such as wounding, methyl viologen and hydrogen peroxide having a herbicial activity by generating active oxygen, NaCl, methyl jasmonate, abscisic acd, low temperature of 15° C. and high temperature of 37° C., etc.
Thus, the present inventors have separated genomic DNA from a sweetpotato which is coding peroxidase expressed actively not only by biological stress but also by many other physical or chemical stresses, and completed this invention by confirming that a promoter of the same is valuable enough in industry.